Our invention pertains to a device to be interposed between an internal combustion engine and a power train, as of off-highway vehicles, for damping the output torque fluctuations of the engine and preventing resonance in the power train.
The transmission of engine output torque to the power train through a damper of the type under consideration has been common with industrial and construction vehicles. The damper of typical known construction comprises a drive plate and a retaining plate rigidly connected to each other and to the flywheel of a vehicle engine for simultaneous rotation therewith, and a driven plate mounted between the drive and retaining plates and connected to the vehicle power train. A spring-loaded friction plate lies between the retaining and driven plates, and another friction plate lies between the drive and driven plates, for frictionally transmitting the engine torque from the drive to the driven plate. A slip occurs between the drive and driven plates upon engine torque fluctuation, resulting in the compression of torsional springs mounted therebetween for absorbing torque fluctuations.
An objection to the prior art damper concerns its spring-loaded friction plate. This friction plate has a planar contact surface held against the driven plate under the bias of a disc spring. Since the disc spring acts on the center portion of the friction plate, however, its contact surface makes frictional engagement with the driven plate under uneven pressure, the peripheral portion of the contact surface receiving significantly less spring pressure than does its central portion. This results in decrease in hysteresis torque (friction torque) and in uneven wear of the friction plate.
Another objection is directed to the second mentioned friction plate, which is urged by the drive plate into frictional contact with the driven plate. The second friction plate has a relatively small area of contact with the driven plate. The damper will have a higher torque fluctuation absorbing ability if the frictional contact area is increased.